ELECTRONIC SPIN BASED ENHANCEMENT OF MAGNETOMETER SENSITIVITY

• US 20100315079A1
• Filed: 12/03/2008
• Published: 12/16/2010
• Est. Priority Date: 12/03/2007
• Status: Active Grant

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Jiang, Liang, Yacoby, Amir, Walsworth, Ronald L., Childress, Lillian, Capellaro, Paola, Taylor, Jake, Lukin, Mikhail
• Granted Patent: US 8,547,090 B2
• Time in Patent Office: Days
• US Class Current: 324/244.1
• CPC Class Codes: G01N 24/10 by using electron paramagnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01R 33/032 using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
• CPC Class Codes: G01R 33/1284 Spin resolved measurements; Influencing spins during measurements, e.g. in spintronics devices G01R33/093 takes precedence; semiconductor devices using spin polarized carriers H01L29/66984
• CPC Class Codes: G01R 33/24 for measuring direction or magnitude of magnetic fields or magnetic flux
• CPC Class Codes: G01R 33/60 using electron paramagnetic resonance G01R33/24, G01R33/62 take precedence

Abstract

A method is disclosed for increasing the sensitivity of a solid state electronic spin based magnetometer that makes use of individual electronic spins or ensembles of electronic spins in a solid-state lattice, for example NV centers in a diamond lattice. The electronic spins may be configured to undergo a Zeeman shift in energy level when photons of light are applied to the electronic spins followed by pulses of an RF field that is substantially transverse to the magnetic field being detected. The method may include coherently controlling the electronic spins by applying to the electronic spins a sequence of RF pulses that dynamically decouple the electronic spins from mutual spin-spin interactions and from interactions with the lattice. The sequence of RF pulses may be a Hahn spin-echo sequence, a Can Purcell Meiboom Gill sequence, or a MREV8 pulse sequence, by way of example.

Claims

1. A magnetometer for detecting a magnetic field, comprising:

an optical system configured to collect and transmit therethrough photons of optical radiation;

a sample containing one or more electronic spins within a solid state lattice, the electronic spins substantially free of interaction with the solid state lattice;

wherein the electronic spins are configured to undergo a Zeeman shift in energy level when photons of excitation light are applied to the electronic spins followed by photons of RF radiation, the Zeeman shift being proportional to the magnetic field; and

a detector configured to detect output optical radiation from the electronic spins, after they have been exposed to the photons of excitation light and RF radiation, and to detect the Zeeman shift from the output optical radiation so as to determine the magnetic field.

2. The magnetometer of claim 1, wherein the sample comprises one of:

a nanocrystal; and

a bulk diamond sample.

3. The magnetometer of claim 1, wherein the optical system comprises an optical waveguide, and wherein the sample is attached at the end of the optical waveguide.

4. The magnetometer of claim 1, further comprising an optical source configured to generate the optical radiation that causes the electronic spin to align along a direction.

5. The magnetometer of claim 4, wherein the optical source comprises a laser.

6. The magnetometer of claim 1, wherein the solid state lattice comprises a diamond lattice, and wherein the electronic spins comprise NV (Nitrogen vacancy) centers.

7. The magnetometer of claim 2, wherein the nanocrystal is a diamond and has a diameter between about 5 nanometers to about 50 nanometers, and wherein the sensitivity of the magnetometer is better then about 1 micro T Hz⁻

1/2.

8. The magnetometer of claim 1, further comprising an RF source configured to generate the RF radiation.

9. A method of increasing the sensitivity of a magnetometer configured to detect a magnetic field, the magnetometer including a plurality of electronic spins that are disposed within a solid state lattice and are configured to undergo a Zeeman shift in energy level when photons of light are applied to the electronic spins followed by pulses of RF radiation, the method comprising:

applying a sequence of RF pulses to dynamically decouple the electronic spins from mutual spin-spin interactions and from interactions with the lattice.

10. The method of claim 9, wherein the magnetic field is aligned along an axis, and at least some of the RF pulses are configured to cause one or more of the electronic spins to rotate around the magnetic field.

11. The method of claim 9, wherein at least some of the RF pulses are configured to cause one or more of the electronic spins to transition to a different spin state.

12. The method of claim 9, wherein the sequence of RF pulses comprises at least one of:

a Hahn spin-echo sequence; and

a Carr Purcell Meiboom Gill sequence.

13. The method of claim 9, wherein the sequence of RF pulses comprises a MREV8 pulse sequence.

14. A method of detecting a magnetic field, comprising:

applying optical excitation radiation to a solid state electronic spin system that contains a plurality of electronic spins within a solid state lattice, thereby aligning the electronic spin with the magnetic field;

applying one or more pulses of RF radiation to the aligned electronic spins so as to induce a precession of the electronic spins about the magnetic field to be sensed, the frequency of the precession being linearly related to the magnetic field by the Zeeman shift of the electronic spin energy levels;

coherently controlling the electronic spins by applying a decoupling sequence of RF pulses so as to decouple the electronic spins from mutual spin-spin interactions and from interactions with the lattice; and

detecting output optical radiation from the solid state electronic spin system after the electronic spins have been subject to the optical excitation radiation and the RF radiation, so as to determine the Zeeman shift and thus the magnetic field.

15. The method of claim 14, wherein the sequence of RF pulses comprises at least one of:

a Hahn spin-echo sequence;

a Carr Purcell Meiboom Gill sequence; and

a MREV8 pulse sequence.

16. A vector magnetometer for detecting a magnetic field that is aligned with one of the crystallographic axes of a solid, the vector magnetometer comprising:

a macroscopic sample of the solid that includes a crystal lattice and a relatively high density of electronic spins within the lattice;

wherein the electronic spins are substantially free of interactions with the lattice;

an optical source configured to generate optical excitation radiation that causes the electronic spins to align with the magnetic field when the optical radiation is applied to the electronic spins;

an RF (radiofrequency) source configured to generate pulses of an RF field that induce a precession of the electronic spins about the magnetic field to be sensed, the frequency of the precession being linearly related to the magnetic field by the Zeeman shift of the electronic spin energy levels; and

a detector configured to detect output optical radiation from the solid state electronic spin system after the optical radiation from the optical source and the RF radiation from the RF source have been transmitted through the electronic spins;

wherein the RF source is further configured to apply the RF radiation only to electronic spins that are aligned along one or more predetermined crystallographic axes.

17. The vector magnetometer of claim 16, wherein the RF source is further configured to change the direction of the RF field in between one or more measurements performed by the magnetometer.

18. The vector magnetometer of claim 16, wherein the RF source is further configured to apply the RF radiation only to electronic spins that are aligned along predetermined quantization axes.